The invention relates generally to seismic exploration systems and, more particularly, to fiber optic seismic exploration systems.
In conventional seismic exploration systems, several hundred to a thousand seismic sensor groups, each composed of one or more individual sensors or geophones, are utilized to obtain seismic data. Usually a sensor group will contain one to thirty geophones electrically interconnected to form a single data channel. Conventional systems utilize a multiconductor seismic cable containing many conductor pairs, one pair for each sensor group, to transmit the seismic data from the sensor groups to a multichannel data processing and recording unit. As these conventional cables are extremely heavy and bulky, handling of such cables is very time consuming and, therefore, very expensive.
Recently, the use of fiber optics as a telemetry link for remotely distributed seismic systems has been suggested, for example, see U.S. Pat. No. 4,117,448 to Siems. Siems discloses a fiber optic cable with a set of triple-redundant optical fibers. The fibers are terminated at each end by a cable connector housing a light emitting diode (LED) and a photodetector. Siems suggests the transmission of digital data over the optical fibers. However, as the LED driver circuit and the photodetector amplification circuit are housed within the remote seismic data gathering unit to which the connector is electrically connected, the digital data is not logic compatible. In other words, the signal amplitude of the digital data is much too low to interface directly with standard logic families, such as transistor-transistor logic (TTL), complimentary metal-oxide semiconductor logic (CMOS), and emitter-coupled logic (ECL). Utilization of the arrangement disclosed in Siems is apparently not practical, as the digital data may become attenuated and distorted due to line capacitance, circuit loading, and RFI/EMI pick-up. Such effect results in costly, inaccurate, and unuseful data gathering.
It would be advantageous to provide a standardized seismic cable connector/transceiver which has practical application in a field environment. It would also be advantageous to provide a connector/transceiver which uses digital signal transmission to avoid irreparable attenuation and distortion of control and data signals. These useful results have been achieved by the present invention.